Heating and cooling systems of this type have a refrigerant compressor, a condenser which condenses the refrigerant from gas to liquid, and an evaporator which allows the refrigerant liquid to evaporate back to gas. For those with appreciable heating or cooling power there will be fans to circulate air past the condenser and the evaporator, to increase their efficiency.
The compressors and fans used by such coolers or heaters generate noise when in operation. This may be found objectionable by customers, particularly in quieter environments such as offices, or where large numbers of coolers are found together such as in convenience stores where there may be ranks of cabinet coolers and some display freezers. Often the dominant source of noise for such coolers is the condenser fan, which must be exposed to the outside environment for good cooling performance in a refrigerator, and thus is difficult to isolate acoustically from the customer.
The compressor and condensor fan will operate to bring the cooler interior down to the setpoint cutoff temperature set by the temperature controller and will then switch off, allowing the interior to slowly rise in temperature until it reaches the maximum acceptable interior temperature, when the compressor will turn on again. While the compressor is operating the condensor fan will create noise.
Where the refrigerator is a cabinet cooler one means of reducing condenser fan noise is to increase the temperature setpoint of the refrigerator interior, thus reducing the amount of time that the compressor must operate to bring the interior to down to the setpoint and the operating duty cycle of the fan and hence the average noise level. However this is incompatible with serving product at the ideal consumption temperature, and it does not reduce the peak noise. Another means is to specify fans of different size or operating speed, however this imposes a tradeoff between reduced thermal capacity and efficiency of the refrigeration system or increased bulk and cost. Other means include the use of low-noise fan designs and acoustic baffles, however these have limited efficacy and may reduce performance.
There is therefore a need for a means of minimising objectionable fan noise while people are in the vicinity of the cooler, while maintaining the thermal capacity of the refrigeration system.
U.S. Pat. No. 6,745,581 relates to historic control of a refrigeration system in which the system operates in energy saving mode based on what traffic has gone before. In the energy saving mode the temperature extremes are relaxed. The system includes person detection and door opening detection, and control of lights and fans. The latter is on a timed on/off basis.
The present invention provides a solution to this and other problems which offers advantages over the prior art or which will at least provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein; this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.